RE: [EFM-Copper] discovery and adding pairs...
Hugh pulled me aside, and while threatening to break my legs, cleared something up for me:)
Within the current draft, (somewhere) it indicates that the "write" operation used for the discovery process is an atomic read/write that fails if something has already been written. Such an atomic operation (i.e. can't write to that register if something is already up in the aggregate) is what ensures that PMDs/pairs can be discovered in the future.
Since I was confused, I'll pass my new understanding. Hugh can break my legs and threaten me again if I get it wrong. The basic operation is...
1) When a PMD/pair comes up, the CO-side attempts a write to a register on the CP side.
2) If that write succeeds, then nothing has been written to this aggregate register in the past (its initialized as zero), so this is the first pair to come up in that aggregate.
3) If that write fails, then some pair is already (and currently) active in the aggregate.
4) In either case, a read returns the identifier for that aggregate.
5) If the write had failed, then this identifier can be used to find the aggregate to which this pair should be added.
6) If the write succeeded, the identifier should be recorded for future PMD/pairs to compare against when they initialize.
7) At any point where there are no pairs left in an aggregate, its discovery register must be zero'd out again.
The above process (I believe) addresses my concern, so I think things are ok. However, I still find the text explaining the above process pretty darn confusing.
- Matt
> -----Original Message-----
> From: Towne, Jeffrey R (Jeff) [mailto:jrt@lucent.com]
> Sent: Monday, November 10, 2003 8:46 AM
> To: Matt Squire; stds-802-3-efm-copper@ieee.org
> Cc: Barry O'Mahony (E-mail); Hugh Barrass (E-mail); Michael Beck
> (E-mail)
> Subject: RE: [EFM-Copper] discovery and adding pairs...
>
>
> I agree.
> Most "inverse multiplex" schemes can accomodate adding
> and/or removing members without restarting the aggregate link.
> Why invent a new one that does not have this capability?
>
> Jeff Towne
>
> -----Original Message-----
> From: Matt Squire [mailto:MSquire@hatterasnetworks.com]
> Sent: Sunday, November 09, 2003 9:53 PM
> To: stds-802-3-efm-copper@ieee.org
> Cc: Barry O'Mahony (E-mail); Hugh Barrass (E-mail); Michael Beck
> (E-mail)
> Subject: [EFM-Copper] discovery and adding pairs...
>
>
>
> One of my TR comments against D2.1 (#302) asked for a
> clarification about how the discovery process can add loops
> to an up and running EFM copper interface (10PASS/2BASE). I
> thought I just misunderstood the discovery process because
> it did not seem possible to add a loop to 10PASS/2BASE port
> that is already operational. The response to the comment is
> that I was correct and that its not possible.
>
> Does anyone else find it unacceptable to have to take down
> all pairs to "re-discover" which pairs can be included in an
> aggregate? IMHO, this is a bizarre and unobtainable
> restriction. Pairs, in general, don't come up at the same
> time. They can go away and come back. The discovery process
> we have in place does not take that into account.
>
> Am I out in left field? Do we think this idea of having all
> ports initializing at the same time is at all feasible?
>
> - Matt
>
>